Why should cancer patients in the United States and Canada—and those who love or diagnose them—care about a report about looming water shortages in distant countries such as South Africa and Argentina?

The report is “Fracking: The New Global Water Crisis.” Written by Food and Water Watch, it documents the many ways in which the technology called hydraulic fracturing threatens the world’s vital water resources. That’s because fracking—when combined with horizontal drilling—uses prodigious amounts of water as a high-pressure hose to blow apart bedrock. The goal is to liberate the wisps of oil or bubbles of gas trapped inside.

The gas or oil flows up and out of the bore hole. But in the process, the water used to free it becomes caught within the fractured rock. Entombed a mile or more below the water table, this water is removed from the Earth’s hydrologic cycle and now resides in the geological underworld. Permanently.

It will never again fall as rain. Or irrigate a field. Or cap a mountain with snow. Or flow through an aqueduct to a city full of people with sinks and bathtubs and teakettles and toothbrushes.

In essence, fracking is a hostage exchange program: to release fossil fuel from the subterranean grip of limestone or shale, water takes its place.